Blood-Drawing Device, in Particular for Infants and Small Children or Small Animals

ABSTRACT

The invention relates to a blood taking device ( 1 ), in particular, for newborn babies and small children or small animals, comprising a blood taking vessel ( 2 ), provided on the front end thereof with a cannula ( 5 ) with a sharpened tip ( 4 ), whereby a porous, gas-permeable limiting element ( 8 ) which automatically stops the flow of taken blood, is arranged by pressing in the blood taking vessel ( 2 ) in a defined position. The rear end of the blood taking vessel ( 2 ) is sealed by a plug ( 11 ) which may be temporarily opened for taking blood ( 11 ), which dispenses the taken blood by means of a stroke running in a sealed manner in the blood taking vessel ( 2 ), which empties under pressure at least a part amount of the blood retained before the limiting element ( 8 ).

The invention relates to a blood-drawing device, in particular forinfants and small children or small animals, comprising a blood-holdingreceptacle provided on its front end with a needle having a sharpenedtip.

A blood-drawing device is known from DE 39 32 112 C2, having an outerblood-holding receptacle that is hermetically sealed at its rear end andis sealed at its front end up to the level of a vent port, and thataccommodates a concentrically positioned internal specimen tube. Thespecimen tube is provided on its front end with a needle that may beinserted into the vein of a patient, and at its rear end is in fluidcommunication with the blood-holding receptacle. The needle is fitted toa holder or is Luer fitting that is fixed to a cone for the specimentube. This blood-drawing device composed of an external blood-holdingreceptacle and an internal specimen tube is very bulky, and despite useof transparent material for the blood-holding receptacle and thespecimen tube is not user-friendly, which complicates observation of theblood flow and makes handling cumbersome. In addition, it is difficultto take defined, small specimen quantities for analytical purposes fromthe large quantity of blood drawn.

After drawing venous blood, the detachable holder or Luer needlesupporting the needle must first be carefully removed and disposed of.This entails the risk of needle sticks from the needle, which inaddition is unavoidably wet with blood. The internal, tube- orcapillary-like specimen tube is then removed in order to empty the drawnquantity of blood into the external blood-holding receptacle. Blood islikewise unavoidably drawn out when the specimen tube is removed.

Notwithstanding, this known blood-drawing device is not suitable fordrawing small quantities of blood, in particular from infants and smallchildren or small animals, on account of their other physiologicalconsiderations, in particular the much lower venous pressure. This isbecause the low blood pressure in these patients is not sufficient forthe blood, which initially flows through the cavity of the needle, toflow opposite to the air that is invariably present in the connectedspecimen tube, causing the blood flow in the needle to cease. Therefore,for drawing blood from infants or the like, only the previously removedLuer needle is used, whose cavity in the insert element receives thedrawn quantity of blood. Blood drawing using only the Luer fitting isvery difficult and requires an experienced user. Finally, the residualquantity of blood remaining in the Luer fitting relative to the lowspecimen volume is excessive upon emptying into a specimen vessel, and adefined drawing of a specimen quantity is not possible at all.

The preceding similarly applies when, in particular for avoiding theresidual quantity remaining in the Luer fitting, the Luer fitting isremoved and then only the needle is employed. The blood specimen canthen be emptied directly into a specimen vessel from the open, possiblyalso curved, rear end of the needle. Since it is very problematic tohold a collection vessel below the open end of the needle to enablereliable collection of the blood specimen, one person holds the patientand performs the puncture operation while another person holds thespecimen vessel for receiving the blood.

To improve the drawing of venous blood in infants and premature babies,nursing infants, and small children, it is known from DE 100 603 02 A1to equip a hollow needle or needle, provided on its distal end with asharpened tip, with a blood outlet, laterally angled with respect to thelongitudinal axis of the hollow needle or needle, at the rear, proximalend thereof. The needle is mounted in a holder so that the grip regionbehind the blood outlet provides a possibility for handling or guiding.For blood drawing, a vessel that collects the flowing blood is heldbelow the outlet opening of the needle. Compared to conventionalinjection needles in use, the needle for this blood-drawing devicerequires no special preparations such as breaking off a Luer cone.However, visual inspection of the quantity of blood to be drawn isinadequate at best, since for these blood-drawing devices of limitedsize the handle and/or the finger of a person drawing the blood maysignificantly limit or even completely obstruct the view of the outletopening. Furthermore, as a result of the laterally angled outlet openingthe needle allows optimal blood flow in only one position of use. Asidefrom the fact that manufacture of a curved, laterally angled needle iscomplex, there is also the disadvantage that the higher flow resistancein the needle as the result of the curvature hinders the flow of theblood, which in any case is drawn in only a small quantity.

The object of the invention, therefore, is to provide a genericblood-drawing device that does not have the referenced disadvantages,and in particular to improve the user-friendliness and ease of operationand allow the reliable drawing of even small quantities of blood.

This object is achieved according to the invention by the fact that aporous, air-permeable limiting element that is pressed in in a definedposition and that automatically stops the flow of the drawn blood isprovided in the blood-holding receptacle, and the rear end of theblood-holding receptacle is sealed by a plunger that may be temporarilyvented for drawing blood and that, for delivering the drawn blood to aspecimen vessel by means of a stroke guided in a sealed manner in theblood-holding receptacle, empties under pressure at least a partialquantity of the blood confined upstream from the limiting element. Thisresults in a very compact device that does not require special handingof the needle, so that blood flow may be observed without impairment,there are no blood losses, and precisely defined blood drawing anddelivery of an exact desired specimen quantity are made possible. Theneedle may be designed as one piece with the blood-holding receptacle,or may have a detachable design for connection thereto.

The air-permeable limiting element stops further blood collection onfirst blood contact, i.e. as soon as the specified filling volume isachieved. The limiting element provides an exact volume determinationfor the blood specimen to be collected, since the limiting elementmaintains a defined and unchanged position in the blood-holdingreceptacle, preferably as the result of an internal stop against whichthe limiting element is inserted and pressed in during manufacture. Thisis completely different from the purpose of porous filter elements,known as such, provided in pipette tips, for example. In such cases thefilter element is intended to prevent contamination of the pipette byaerosols, for example, for which contact with the collected liquid isnot desired. In addition, it is not critical for ensuring thefunctionality of such a pipette tip if a defined filter position is notprecisely maintained.

Furthermore, the blood-drawing device according to the invention allowsthe specified quantity of blood collected in the blood-holdingreceptacle, including the interior of the needle, to be expelled in thedesired amount for analysis, since the quantity of blood may be emptiedcompletely, or alternatively with staged metering, by a plunger stroke.The capability for venting the plunger, for example by means of aplunger retainer that fits loosely in the delivered state of theblood-drawing device and therefore in the blood-drawing orblood-collection position, or by means of a vent port in the plunger,preferably at the upper end thereof, provides the venting required fordrawing of the specimen quantity. On the other hand, the required sealbetween the plunger and the vessel housing for forced emptying iscreated by pressure accompanied by discontinuation of the providedventing, specifically, when the plunger is moved from the vented, loosestarting position into the sealed delivery path, or, for a plunger thatis sealed from the outset, when the vent port is closed by a finger.

In one proposal of the invention, the front end of the blood-drawingdevice containing the needle and the limiting element is designed as atube. The tube assists in drawing the blood into the collection chamberof the blood-drawing device that is delimited by the filter element.

Further features and particulars of the invention result from the claimsand the following description of one exemplary embodiment of theinvention, illustrated in the single drawing as a general view in alongitudinal section.

A blood-drawing device 1 illustrated in the figure has a blood-holdingreceptacle 2 that in the illustrated embodiment has on its front end afrustoconically tapered tube 3 holding a needle 5 that has a sharpenedtip 4 and that merges in one piece with a cylindrical section 6 of muchgreater diameter that adjoins it to the rear. The tube 3 is separatedfrom the chamber 7 of the cylindrical section 6 by a porous limitingelement 8 that is pressed against a stop 9 for the blood-holdingreceptacle in a defined manner, and that precisely defines thecollection volume of the tube 3 by virtue of this exact positioning. Assoon as the drawn blood reaches the limiting element 8, intake throughthe needle 5 is stopped. In this way a specimen volume 10 may bedetermined or specified in a very precise manner. As a result of directcontact of the needle 5 with the front end of the blood-drawing device1, in this case the tube 3 in the blood-holding receptacle 2, anycontour transitions that interfere with blood flow or handling areavoided. Since the blood-drawing device 1 is also self-contained, thereis no risk of contamination.

A plunger 11, shown in its starting position for blood collection ordrawing, is provided at the end of the blood-holding receptacle 2opposite the tube 3. For venting during blood drawing, a plunger head 12that moves forward into the cylindrical section 6 is sealed in theblood-holding receptacle 2 from the outset. The plunger maintains thisseal even during movement through its stroke 13 for emptying thecollected quantity of blood, to which end a vent port 14, provided forblood drawing in the shown starting position of the plunger 11, at theupper end thereof, is closed by an operator placing a finger thereoverduring displacement. Alternatively, the plunger head 12 could beprovided with a gap facing the inner vessel wall that, as the result ofa complementary structural design of the mutually facing walls of theplunger head 9 [translator's note: should be 12] and inner wall of thecylindrical section 6, closes when the plunger head 12 enters thedelivery stroke 13.

For drawing a specimen, the collected quantity of blood defined by theabutment of the limiting element 8 in the tube 3, including the interiorof the needle 5, may be expelled by the plunger 12 in a simple manner,preferably as a total metered quantity but also as a partial meteredquantity, into a separate specimen vessel (not shown) into which thespecimen quantity flows through the needle 5. In this manner it ispossible to empty a specimen without residue or losses, which isparticularly important when only small amounts of blood are drawn.

1. A blood-drawing device, in particular for infants and small children or small animals, comprising a blood-holding receptacle provided on its front end with a needle having a sharpened tip wherein a porous, air-permeable limiting element (8) that is pressed in in a defined position and that automatically stops the flow of drawn blood is provided in the blood-holding receptacle (2), and a rear end of the blood-holding receptacle (2) is sealed by a plunger (11) that may be temporarily vented for drawing blood and that, for delivering the drawn blood to a specimen vessel by means of a forward advance guided in a sealed manner in the blood-holding receptacle (2), empties under pressure at least a partial quantity of the blood confined upstream of the limiting element (8).
 2. The blood-drawing device according to claim 1 wherein the front end of the blood-drawing device (2) containing the needle (5) and the limiting element (8) is designed as a tube (3). 